1. Field of the Invention
This invention relates to a power semiconductor device having a semiconductor element located between two main electrodes.
2. Description of the Prior Art
Power semiconductor devices are presently predominantly produced having a semiconductor element pressed between two electrodes and the element forming a sliding contact with the electrodes. For providing a dissipation of the heat generated by the semiconductor system members are attached to the outer surfaces for heat removal. If necessary a cooling liquid such as water, oil and the like can circulate through the members providing for the removal of the heat generated.
The heat transmission resistance of the described semiconductor devices at the contact surface between the electrode block and the member for providing for heat removal does not sink below a certain value, since there is only a limited improvement possible for a sliding contact heat transfer mechanism as provided if an electrode block is pressed against a member for removal of the heat. This results in turn in a limit for the power going through or being controlled by the semiconductor device. In summary, the presence of the pressed contact area results in an impairment of the heat removal from the semiconductor element of its internally generated heat. Therefore it is desirable to remove this contact surface of the electrode and of the cooling member for obtaining a higher rating of the semiconductor device.
Constructions of power transistor devices have been described which eliminate in principle the pressure contact surface. These devices have electrode blocks with suitable hollow spaces in suitable geometric layouts, e.g. with protrusions, pins and the like which serve to provide a circulation path of the cooling fluid. The hollow spaces are sealed with elastic elements and are closed with a cap. However these constructions are complicated and expensive to manufacture and they comprise a larger number of components and furthermore their reliability is not as good as desired.